1. Field of the Invention
This invention relates generally to seat-positioning mechanisms, and is particularly concerned with seat-positioning mechanisms of the type in which a rod or shaft member is pivotally attached to the seat back and slides within a locking mechanism fixedly attached to the seat.
2. Description of the Prior Art
The samples of positioning mechanisms of the general type with which this invention is concerned are shown in U.S. Pat. Nos. 2,595,240; 3,271,071; 3,383,135; 3,356,411; 3,419,306 and 4,099,777.
Many of the mechanisms of this type generally include a pair of elongated members slidably connected for telescopic movement between extended and retracted positions with respect to each other, and one or more friction washers have a locked position in frictional engagement with one of the members to restrain the members against relative movement and an unlocked position permitting free relative movement between the members. The friction washers are generally biased to lock the position, and a release cam or the like is selectively operable to remove the friction washers to the unlocked position against the biasing force. The friction washers engage a fulcrum, and are biased to tilt about the fulcrum to the locked position.
The improved mechanism set forth herein most closely resembles the locking device set forth in U.S. Pat. No. 2,595,240 and is an improvement on that basic design.
In automotive applications, federal law requires that a seat back withstand an inertial load equal to twenty times the forces due to gravity. Consequently, the locking device must be able to lock a shaft having 2,000 to 3,000 pounds of force applied thereto. It has been found that a device similar to that shown in U.S. Pat. No. 2,595,240 cannot withstand forces of this magnitude. It has been left to the present invention to provide a heavy duty, compact and relatively simple device for locking an automotive seat in place by preventing a linear motion of a shaft attached to the seat hinge.